To provide information on the basic process of ATP- transphosphorylation, a comparative physical and chemical approach has been initiated on several enzymes which have in common the ability to catalyze the transfer of the terminal phosphoryl group of ATP to a suitable acceptor, but which differ markedly in their substrate specificity requirements or range of requirements for the acceptor. It is presumed that certain physical and chemical similarities as well as significant differences will manifest themselves in detailed studies of these enzyme proteins and on their catalyzed reactions, so that eventually, a broad picture will emerge and which will permit one to define more clearly the chemical and physical requirements for transphosphorylation as well as to permit a delineation of individual requirements which may be demanded for the specificity functions. To this aim, comparative physico-chemical studies are to be continued or will be undertaken anew on the following series of crystalline enzymes: ATP-AMP transphosphorylase (myokinase) from the muscle and liver of rabbit, calf, and man; the ATP-creatine transphosphorylase isoenzymes (muscle- type, brain-type, and hybrid) from rabbit, calf, normal human tissues and from dystrophic human tissue and finally, nucleoside diphosphokinase (nucleoside diphosphate nucleoside triphosphate transphosphorylase) from yeast. The physico-chemical comparison has thereby been broadened to include the isoenzymes of the ATP-creatine transphosphorylase and of ATP-AMP transphosphorylase from several mammalian species. The enzyme from normal human tissues and from pathological dystrophic tissues will likely be of especial interest to those concerned with the genetic problem of progressive muscular dystrophy in man. B. Studies on TPN- Associated Reactions. An insight into the mechanism of action of the crystalline TPN- glucose 6-phosphate dehydrogenase will be gained by complementing information obtained from studies on the catalyzed reaction with physical and chemical studies on the protein catalyst and on its substrates. Since via a comparative attack (similar to the studies on the ATP- transphosphorylases), information may be arrived at the fundamental problem of catalytic dehydrogenation and oxidation, the glucose 6- phosphate dehydrogenase will also be studied from sources other t (Text Truncated - Exceeds Capacity)